A pinch of salt dramatically improves the performance of batteries

It turns out that salt is more than just a versatile condiment: Researchers found that salt can also be used to significantly boost the performance of batteries.

The research teams from the Max Planck Institute for Solid State Research, Queen Mary University of London, and the University of Cambridge discovered that once salt is added to a supermolecular sponge and baked at a high temperature, the sponge turns into a carbon-based structure. They were surprised to observe that the combination can trigger a special reaction that can turn a homogeneous mass into an “intricate structure with [fibers], struts, pillars and webs.”

Carbon is a family of the most versatile materials in nature, and it is often used in catalysis and electronics due to its conductivity, as well as chemical and thermal stability. Examples of carbon forms are graphene and carbon nanotubes, which are similar to the graphite in pencils and are good conductors of electricity.

In the study, which was published in the Journal of the American Chemical Society (JACS), the researchers showed that using these materials in lithium-ion batteries can let batteries charge quickly. Additionally, the salt ensured that the batteries are “at one of the highest capacities.” (Related: Praise for the proton: Latest battery breakthrough may free us from lithium ion.)

The researchers used a supermolecular sponge called a metal organic framework (MOF) material for the study. MOFs are “attractive, molecularly designed porous materials” that have various promising applications, like gas storage and separation. Since MOFs can retain high surface area even after carbonization (meaning they are baked at a high temperature), they can potentially be used as electrode materials for batteries.

The researchers refer to the structures as “nano-diatoms” due to their intricate architecture. They posited that the nano-diatoms have potential use for energy storage and conversion, e.g., as electrocatalysts for hydrogen production.

Prior to the study, carbonizing MOFs has preserved the structure of the initial particles similar to that of a dense carbon foam. But when salts are added to MOF sponges and the latter are carbonized, the researchers discovered a series of carbon-based materials with multiple levels of hierarchy.

Dr. Stoyan Smoukov, the lead author and project leader from Queen Mary’s School of Engineering and Materials Science, commented that the transformation only occurred when the compounds were heated to 800 degrees Celsius. He added that they were pleased to figure out how to use chemical composition to control the transformations.

The researchers explained that this type of 3D hierarchically organized carbon structure can be extremely hard to culture in a laboratory. However, the structure is important when it comes to giving “unimpeded ion transport” to a battery’s active sites.

Dr. R. Vasant Kumar, a researcher from the University of Cambridge, said that their work can be used to further the use of MOFs. He added that the strategy they devised for structuring carbon materials could have significant applications for energy storage along with energy conversion and sensing.

Tiesheng Wang, the lead author from the University of Cambridge, concluded that researchers could design nano-diatoms with “desired structures and active sites incorporated in the carbon” since there are thousands of MOFs and salts that they can experiment with.

The 3D carbon-based nanostructures, with multiple levels of hierarchy formed when salt is added to a supermolecular sponge, can retain its useful physical properties, such as good electronic conductivity.

The nanostructures have other unique properties: they can have “improved wettability (to facilitate ion infiltration), high strength per unit weight, and directional pathways for fluid transport.”

While it can be difficult to create carbon-based multilevel hierarchical structures, especially through simple chemical routes, these structures could have endless potential. If the materials can be produced in large quantities, they can be utilized for industrial purposes.

Learn more about other findings on battery performance at Research.news.

Sources include:

ScienceDaily.com

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